Is ther in Asterisk CLI any log to see that email with attached file included voicemail are sent to user?
I see only that .wav file is created but not it was sent.
That will be logged by the Mail Transport Agent, e.g. sendmail, not by Asterisk, itself.
Assuming you are using Postfix, This one logs all failed and successful deliveries to a logfile. The file is usually called /var/log/maillog or /var/log/mail; the exact pathname is defined in the /etc/syslog.conf file.